<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>回调函数</title>
	<script type="text/javascript">
		var fn = function(){
			console.log(123);
		}
		setTimeout(fn,1000);
		console.log(456);
	</script>
</head>
<body>

</body>
</html>